Magnetoelastic force transducers are previously known from, for example, Swedish Pat. No. 151 267. Such a transducer comprises a force-subjected magnetic core built up of magnetoelastic sheets, which core is provided with four through-holes for two windings located perpendicular one to the other, one winding being an excitation winding adapted to be connected to an a.c. source for generating a magnetic flux in the core, and the other winding being a measuring winding for sensing the magnitude of the magnetic flux passing through the measuring winding. The magnitude of this flux depends on the magnitude of the external force applied to the core.
The design principle with a magnetic core built up of magnetoelastic sheets has--since the evolution of the design featured in Swedish Pat. No. 151 267--been developed and sophisticated in several respects to provide force transducers with improved performance.
An example of the latter is disclosed in European Pat. No. 0 089 916. This shows a magnetoelastic force transducer with a specially formed sheet section with a measuring part formed as a double-bent beam. Such a transducer exhibits very good performance as far as linearity and zero voltage values are concerned.
From the point of view of manufacture, however, the transducers described above require considerable resources in terms of tools for sheet metal forming, punching, winding, gluing, etc.. This also means that these transducers are relatively expensive, in particular in applications where there are no extreme demands for performance. Therefore, from various quarters there has been a long-felt need for a simple, robust and relatively inexpensive force transducer, which is favourable from the manufacturing point of view, for use in installations where the demands for linearity, zero residual voltage, etc., are not too severe.
A magnetoelastic force transducer according to the invention has a constructive design which makes it extremely well suited for automatic series production. This means, inter alia, that the manufacturing costs are considerably lower than for prior art designs.